This invention relates to an ignition apparatus and method for igniting relatively lean fuel/air mixtures in a primary combustion chamber. More particularly, the invention relates in one embodiment of the invention, to an ignition apparatus that may be retrofitted into a conventional internal combustion engine, whether gas, diesel, or the like, to significantly improve the amount of energy that can be extracted from a fixed unit of fuel.
A common problem associated with any system that relies upon the burning of fuel as a source of energy is efficiently igniting the fuel so that a maximum amount of energy can be derived therefrom. This is especially a problem in an internal combustion engine (and similar applications), where the fuel must be rapidly burned so as to transfer maximum energy to the piston. For this reason, careful selection and maintenance of the fuel/air ratio and the octane rating of the particular fuel that is used are extremely important considerations for the efficient performance of a conventional spark-ignition internal combustion engine. Likewise, the cetane rating of diesel fuel becomes a very important factor for efficient performance of a conventional diesel engine.
It is commonly known that no more heat energy can be derived from a high-octane or high-cetane fuel than can be derived from a low-octane or low-cetane fuel. This is because octane and cetane merely refer to a measure of the auto-ignition characteristics of the gasoline or diesel fuel respectively. Thus, a low-octane (or low-cetane) fuel is simply more difficult to ignite than a high-octane (or high-cetane) fuel. The use of a low-octane fuel in a spark ignition engine, for example, may result in "knocking," which simply means that some of the highly compressed fuel in the cylinder (which should have been ignited but for the poor auto-ignition characteristics of the fuel) is compressed even more by the flame front moving out from the spark plug. As this compressed fuel continues to be compressed against the walls of the combustion chamber, or other similar combustion chamber, it acts as a hot moving piston that "knocks" against the combustion chamber wall. Such knocking, commonly referred to as detonation, is not only inefficient (because not all of the fuel in the cylinder is being burned) but it can also inflict serious damage to the engine. A similar problem to "knocking" occurs when a low-cetane fuel is ignited in a diesel engine, the low cetane rating delaying the time at which the fuel ignites and thereby producing combustion pressures not synchronized nor compatible with optimum performance of the engine. Unfortunately, as is well known, the refining of high-octane and high-cetane fuels is more costly and not as efficient (that is, there are not as many gallons that can be refined from a given amount of crude oil) as the refining of low-octane or low-cetane fuels. Thus, the use of high-octane and high-cetane fuels by most modern internal combustion engines presents some "built-in" innefficiencies relative to the ever decreasing supply of available crude oil.
An additional problem associated with the operation of conventional spark-ignition internal combustion engines is maintaining the correct fuel/air ratio to insure the efficient ignition of the fuel. This is because the relatively low ignition efficiency of a conventional spark plug requires a relatively rich fuel/air mixture in order to sustain ignition. Accordingly, it is customary to provide an excess of fuel solely for ignition purposes. A typical fuel/air ratio, for example, may be about 1:8 (1 part vaporized fuel to 8 parts air). However, this fuel/air ratio is substantially in excess of an optimum fuel/air ratio for the appropriate combustion and expansion of the combustion products in the cylinder. It is currently believed that an optimum fuel/air ratio for combustion may be as low as 1:40. Thus, the use of a fuel/air ratio for ignition purposes that contains 4 or 5 times as much fuel is as really needed for optimum combustion is terribly inefficient.
While there have been some prior art attempts to improve the inefficiencies caused by the relatively rich fuel/air ratios required by conventional spark-ignition engines, such as that disclosed in U.S. Pat. No. 4,096,832 (1978) (wherein this inventor was a joint inventor), including the "stratified charge" systems described in that patent, there has been little disclosed in the prior art of which this inventor is aware to improve the "built-in" inefficiencies that result from having to use high-octane and high-cetane fuels. Moreover, the continued use of conventional gasoline and diesel fuel may in itself be somewhat of a "built-in" inefficiency for the operation of most hydrocarbon powered engines. This is because many other fuel types may be more readily available or produceable, or could be more efficiently refined from the same amount of crude oil, than the ubiquitous gasoline and diesel fuels. Such other fuels would include alcohol, kerosene, coal oil, hydrogen, methane, and producer gas.
It would, therefore, be an improvement in the art to provide a fuel ignitor that would not only efficiently ignite a lean fuel/air mixture, but that would also be useable with lower-octane and cetane fuels, or other types of fuels that are more readily available and less expensive to produce. It would be a further improvement in the art if such a fuel ignitor could not only be retrofitted into an existing gasoline or diesel engines, but also useable for a wide variety of applications that require the efficient combustion of a fuel contained in a primary combustion chamber. Such an invention is disclosed and claimed herein.